Adhesive interactions among leukocytes and between leukocytes and endothelium are central to processes of inflammation. These interactions are mediated by sequential molecular steps involving carbohydrates and selectins, and integrins and ICAMs. We used flow cytometry to examine the interaction of neutrophils with cells transfected with ICAM, a counter structure for the neutrophil integrins. A manuscript has been submitted (Simon). We extended this approach to examine the mechanisms of aggregation of lymphoma cells which may contribute to leukostasis. A manuscript has been published in Blood (Larson) In Year 16, we have begun to compare selectins of different lengths (McEver and Edwards) for their ability to support cell adhesion under conditions of defined shear using adhesion produced in a cone and plate visoometer and flow cytometric analysis. We have also begun to examine the binding of soluble selectins to native cell surface mucins. Pilot data suggest that the dissociation of soluble P-slelectin from the mucin PSGL occurs on the second time frame. Bruce Edwards has become affiliated with the NFCR by joining the faculty at UNM. A new project is being developed to use oligonucleotide ligands to selectins (Parma) to study the activity and topography of cell surface adhesion receptors with resonance energy transfer and rapid mix flow cytometry.